Glyphosate is commonly used and distributed as an aqueous solution of a glyphosate salt such as the isopropyl ammonium, potassium or ammonium salts.
In order to reduce the transport and handling costs associated with glyphosate concentrates it is desirable to use a high loading of glyphosate, that is, the amount of active (usually expressed as glyphosate acid equivalent per liter of aqueous formulation) is desirably high within the bounds of the solubility and ability to conveniently pour and dilute the concentrate.
U.S. Pat. No. 6,544,930 (Wright) reports that high loadings can be achieved using the potassium salt of glyphosate and compositions of the potassium salt are available at loadings of 540 g acid equivalent (ae) per liter of aqueous formulation.
International Patent Publication No. WO 01/26469 discloses that aqueous formulations of glyphosate, including highly concentrated formulations, can be prepared using a mixture of glyphosate isopropyl amine and ammonium salts particularly in a weight ratio (expressed on a glyphosate a.e. basis) of 80:20 to 97:3.
U.S. Pat. No. 6,881,707 (Howat and Hay) reports a glyphosate composition comprising a mixture of salts of glyphosate comprising each of potassium and isopropylammonium salts. International Publication WO2006/023431 asserts that loadings of at least about 400 g glyphosate acid equivalent can be obtained by formulating in aqueous solution a mixture of salts of glyphosate at a total glyphosate a.e. concentration not less than about 360 gae/L, wherein (a) said glyphosate is in anionic form accompanied by low molecular weight non-amphiphilic cations in a total molar amount of about 100% to about 120% of the molar amount of said glyphosate; (b) said cations comprise potassium and propylammonium (e.g., IPA) cations in a mole ratio of about 70:30 to about 90:10; and (c) said potassium and propylammonium cations together constitute about 90 to 100 molar percent of all of said low molecular weight non-amphiphilic cations in the composition. The patent reports formulations of up to 590 g glyphosate acid equivalent per liter of aqueous formulation.
The concentrate formulation of glyphosate can be difficult to handle due to viscosity, particularly at low temperatures and high loadings of active. At high loadings the viscosity of the composition is increased to such an extent that it is often difficult to dispense the aqueous solution by pouring or pumping with normal pump equipment. Also the solution stability of the salts may be compromised, particularly at low temperatures so that precipitates form at low temperature which can not be readily resuspended or solubilised.
The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.